I. Technical Field
The present invention relates to dust-removing apparatuses applied to, for example, integrated gasification combined cycle (IGCC) facilities and pressurized fluidized-bed combustion (PFBC) combined cycle facilities, particularly, to a dust-removing apparatus that repeats a backwash operation, in which a high-pressure medium is supplied and stopped, with high frequency and that controls the operation with valves.
II. Description of the Related Art
As a system for removing dust from a dust-containing gas, for example, a candle-type porous filter system is known in the related art. This porous filter system collects and removes dust from gas passing through porous filter elements. Therefore, as caked dust collected on the filter surfaces of the porous filter elements grows, it increases the flow resistance, thus raising the differential pressure of the porous filter elements (filter differential pressure).
To decrease the differential pressure of the porous filter elements for continuous operation of the system, therefore, a backwash system needs to be operated in which backwashing is performed by blowing a high-pressure gas into the outlets of the porous filter elements to release and remove dust deposited on the surfaces of the porous filter elements.
In a known example of a porous filter system shown in FIG. 7, reference sign 10 in the figure is a porous filter (dust-removing apparatus), reference sign 12 is a vessel body, reference sign 14 is a porous filter element, reference sign 16 is a filter tube sheet, reference sign 18 is a dust-containing-gas introduction pipe, reference sign 20 is a clean gas outlet, and reference sign 22 is a dust discharge outlet. This porous filter 10 is configured such that a dust-containing gas is introduced from the dust-containing-gas introduction pipe 18 into the vessel body 12, passes through the porous filter elements 14, which are provided in large numbers, and flows out of the vessel from the clean gas outlet 20. As the dust-containing gas passes through the porous filter elements 14, therefore, the dust, being composed of particles, is separated from the gas without being able to pass through the porous filter elements 14 and is deposited and collected on the filter surfaces of the porous filter elements 14.
In addition, a backwash system for releasing and removing caked dust deposited and grown on the filter surfaces of the porous filter elements 14 is configured to blow a high-pressure gas into backwash nozzles 34 through a main backwash pipe 31 connected to high-pressure-gas supply equipment 30 such as a compressor. That is, the backwash system for the porous filter 10 can blow a high-pressure gas into the outlets of the porous filter elements 14 (clean gas outlets) in a direction opposite to the flow direction of the dust-containing gas to release and remove caked dust deposited on the filter surfaces by means of the flow of high-pressure gas.
In the example structure shown, for continuous operation within a process, the filter group, composed of the large number of porous filter elements 14 installed in the vessel body 12, is divided into a plurality of (in the example shown, four) cleaning areas, and four backwash pipes 32a, 32b, 32c, and 32d branched off from and independent of the main backwash pipe 31 are provided for the respective groups of the cleaning areas. The backwash pipes 32a, 32b, 32c, and 32d have backwash valves 36a, 36b, 36c, and 36d, respectively.
The opening/closing operation of the backwash valves 36a, 36b, 36c, and 36d is managed such that regular backwashing is executed for each group or for each set of several separate groups so that the flow of the dust-containing gas through the vessel body 12 of the porous filter 10 shows less variation. The backwash pipes 32a, 32b, 32c, and 32d and the backwash valves 36a, 36b, 36c, and 36d are collectively referred to as backwash pipes 32 and backwash valves 36, respectively, unless the cleaning areas need to be distinguished.
As a known backwash apparatus using compressed gas, on the other hand, one composed of a compressed gas source and a gas reservoir space having valves on the upstream and downstream sides thereof is disclosed in Publication of Japanese Patent No. 3128261 below. This backwash apparatus is configured such that a high-response-speed valve is used as the downstream valve to remove all dust deposited on ceramic filter tubes with a short pulse.    Publication of Japanese Patent No. 3128261